Postpartum Depression is a serious disorder, affecting approximately 10% to 15% of women after delivery. The identification of risk factors is an important research goal, and some of the most important predictors include stress and a history of depression. A biological system that has not received appropriate attention in this context is the hypothalamus-pituitary-adrenal axis. During pregnancy, the regulation of this important stress-responsive system is drastically altered. Specifically, corticotropin releasing hormone (CRH) is released into the maternal and fetal blood stream by the placenta, resulting in exponential CRH increase as pregnancy progresses. Higher placental CRH (pCRH) levels are predictive of pre-term birth, and it has been suggested that changes in pCRH throughout pregnancy and the postpartum period may play a role as a predictor of postpartum depression, particularly around 25 weeks gestation. To further elucidate the role of pCRH as a predictor of postpartum depression, it is necessary to first understand what it is that leads to accelerated pCRH increases in some women. The aims of the present study therefore are (a) to determine whether stimulated HPA axis activity predicts pCRH levels, and (b) to determine whether stress and depressive mood predict pCRH levels. Seventy women will be investigated at 10-12 weeks and again at 24-26 weeks gestation in a prospective study design. At both visits, pCRH levels will be assessed. Cortisol responses and self-report of stress responses to an acute laboratory stressor will be measured at both time points, and will be used as indicators of stress vulnerability. Three markers of "depression" will be used: a psychiatric diagnosis (SCID), a self-report measure (CES-D), and an indirect measure of depressed mood (Emotional Stroop Test). [The Emotional Stroop Test is not sensitive to a participant's willingness to disclose negative emotion, and will therefore provide an important complement to the findings obtained with the two more traditional measures of depression.] This research is important because it will (a) advance the understanding of biobehavioral mechanisms leading to increased pCRH, and ultimately to postpartum depression, and (b) contribute to the identification of risk factors and thus to the development of early intervention programs. PUBLIC HEALTH RELEVANCE: This project is relevant to public health because it will provide important information about biological and psychosocial factors early in pregnancy that put some women at risk for the development of postpartum depression. Knowledge about early risk factors is essential because it provides a sound background for the development of effective and timely preventative and therapeutic interventions aimed at high risk populations.